1. Field of the Invention
The invention relates to fasteners and in particular to indicia applied to fasteners for tracing certain manufacturing information for individual fasteners. More particularly, the invention is directed to a method of applying such indicia to fasteners in an efficient manner while minimizing the purchase and inventory of tooling required for applying the indicia.
2. Background Art
In recent years, purchasers of fasteners increasingly have demanded that certain manufacturing information relating to a fastener be traceable using codes or the like. This demand has been driven primarily by product liability law, inasmuch as industries such as automotive and construction realize that such traceability will place them in a stronger position in a liability suit directed at one of their products, if it can be proven that all components in the product were made to proper specifications.
Heretofore, most fastener manufacturers have offered a tracing system in which codes typically are applied to a container such as a box or bin holding many fasteners. More particularly, a label attached to the fastener container typically displays information such as a laboratory and/or order number from which certain information about the fasteners can be traced, such as material, performance and manufacturing data. Such data can include date of manufacture, the material used in manufacture, lot certification, and heat treatment and statistical process control data. This information typically is maintained by the fastener manufacturer for at least five (5) years, in accordance with product liability law requirements.
However, such a label-driven tracing system is particularly cumbersome for a purchaser of the fasteners. This is because once an individual fastener is removed from its container for use such as in a product, the fastener user must record and maintain the container label information if it ever hopes to trace the origin of the fastener should a product failure or question about the fastener itself occur. Many industries thus now are demanding that responsibility for fastener tracing code recording/maintenance be transferred to the fastener manufacturer. In response to this demand, many fastener manufacturers have begun to apply tracing indicia directly to the fastener in the form of, for example, a three-digit code stamped into the head or shank of the fastener. Such a direct marking system facilitates traceability without burdensome information recording/maintenance by a product manufacturer for each fastener used. Direct marking also improves manufacturing processes for fastener manufacturers since it can eliminate costly and time consuming packaging of fasteners in boxes or the like which heretofore had to be labeled for traceability.
However, a problem also exists with direct marking of fasteners. More particularly, a plurality of code characters such as numbers and/or letters typically must be applied to a fastener to provide enough information for tracing. Since most industrial-grade fasteners are made of a hard material such as steel, special tools must be used to impress the indicia into the finished fastener. The conventional tools typically used to directly mark a fastener in such a manner are either a forge stamp for impressing indicia into a flat fastener surface, or a roll stamp for impressing the indicia into a curved fastener surface such as the shank of a bolt or the side of a head of a bolt. Unfortunately, forge stamps and roll stamps must be custom made either in a die, by forging or by pressing, and thus can be relatively expensive, and wear out fairly quickly due to their use on hard fastener surfaces. Therefore, it can be understood that a plurality of forge or roll stamps may be needed to mark a single manufacturing run or lot of fasteners. Moreover, most fastener producers manufacture many lots of a certain fastener during any given time period, usually a year, and since each lot must obviously be identified differently for tracing purposes, it can be appreciated that many stamping tools bearing different indicia must be purchased prior to fastener manufacture and held in inventory. Also, since it is difficult to predict how many fastener lots will be made in a given year or how large the lots will be, many stamping tools often are wasted since it is possible that a lot may be smaller than the number of identical stamping tools ordered for that lot, or that in a given year less lots will be manufactured than different stamping tools ordered for those lots.
The method of the present invention solves the above-described possible problem of excess purchase and inventory of costly fastener identification tooling, by selectively removing one or more of a plurality of code characters from a marking tool, and thereby making that tool universal for use with multiple lots in any given time period.